Uomo avvisato, mezzo salvato.
Literally: Man warned, half saved
The English version is “Forewarned is forearmed”. In other words, having advance knowledge of something gives you an advantage. The Italian version refers to being “half saved”, in that the warning goes some way to helping you out of a potential difficulty. This reminds me of the English saying “Knowing/understanding the problem is half the solution,” which has a similar meaning.